Screw.



A. UMHOLTZ.

SCREW.

APPLICATION IILED JAN. 9, 1909.

m a P w m m m 9 Specification of Letters Patent. Patented Sept. 1%,1909. Application filed January 9, 1909. Serial No. 471,383.

To all whom it may concern:

Be it known that I, AUGUSTUS UMHoLrz,

a citizen of the .United States, residing at- Magnolia, in the county ofCamden and State of New Jersey, have invented certain new and usefulImprovements in Screws, of which the following is a specification.

My invention relates to improvements in screws, and more particularly towood screws, theobject .of the invention being to so construct the headof the screw, that the head will afford the maximum of resistanceagainst the indrawing of the head by the threads of the screw, and hencesecurely bind the wood back of the head.

With this object in view, the invention consists in a screw having ahead of annular stepped formation, providing a series of annular fiatfaces to bear against the wood.

In the accompanying drawings, Figure 1, is a view in elevationillustrating my improvements. Fig. 2, is a view in longitudinal section,and Fig. 3, is an enlarged view of the screw head when forced into thewood.

1 represents the shank of the screw having the ordinary screw threads 2,and provided with my improved head 3. This head 3 is so shaped as toform a series of annular fiat faces el. In other words, the head of thescrew has a general stepped formation to resist inward movement of thehead in the wood, and compel the threads to exert great power, andtightly press the wood between the threads and the head.

In soft wood, the head of the screw would countersink itself, but wouldafford a great amount of resistance to such countersinking, and henceeffectually bind the wood. In hard wood, a countersinking too] wouldhave to be employed, but this would not prevent the flat faces orstepped form of the ment of the head, and hence tightly binding thewood.

I am aware that screw heads have been made with grooves, but suchgrooving and shaping of the heads has been to accelerate thecountersinking of the head, whereas the purpose of my construction istooppose the countersinking and compel greater clamping wower on thescrew threads to draw the head in the wood.

Having thus described my invention what- I claim as new and desire tosecure by Letters Patent isz,

As an article of manufacture, a screw having a head of general taperingform thereon, and formed with a series of annular grooves, one wall ofeach groove extending in lines at exact right angles to the longitudinalaxis of the screw, the other walls of said grooves extending inlinesparallelwith the longitudinal axis of the scren and the portionsbetween said grooves beveled, substantially as set forth.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

AUGUSTUS UMHOLTZ.

\Vitnesses HARRY P. UMHoL'rz, MARY J. UMIIOLTL head from holding backthe inward move--

